To add a new NOT NULL column to an already created table, use ALTER command. Let us first create a table −
mysql> create table DemoTable -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(20) -> ); Query OK, 0 rows affected (0.60 sec)
Following is the query to add a new NOT NULL column to an existing table −
mysql> alter table DemoTable add column StudentAge int NOT NULL; Query OK, 0 rows affected (0.52 sec) Records: 0 Duplicates: 0 Warnings: 0
Insert some records in the table using insert command −
mysql> insert into DemoTable(StudentName,StudentAge) values('Chris',21); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(StudentName,StudentAge) values('David',23); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable(StudentName,StudentAge) values('Mike',NULL); ERROR 1048 (23000): Column 'StudentAge' cannot be null
Display all records from the table using select statement −
mysql> select * from DemoTable;
This will produce the following output −
+-----------+-------------+------------+ | StudentId | StudentName | StudentAge | +-----------+-------------+------------+ | 1 | Chris | 21 | | 2 | David | 23 | +-----------+-------------+------------+ 2 rows in set (0.00 sec)